Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
  • A61L31/14—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
  • A61L31/148—Materials at least partially resorbable by the body
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
  • A61L31/14—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
  • A61L31/16—Biologically active materials, e.g. therapeutic substances
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
  • A61L2300/40—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices characterised by a specific therapeutic activity or mode of action
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2430/00—Materials or treatment for tissue regeneration
  • A61L2430/02—Materials or treatment for tissue regeneration for reconstruction of bones; weight-bearing implants

Definitions

• the present invention relates generally to the treatment of disorders of skeletal tissue, to its regeneration and remodeling, and specifically, to devices and methods for inhibiting bone resorption and improving bone formation, in the form of fixation devices or supporting a prosthetic implant.
• the basis of enhancing bone repair and regeneration is based principally on the use of 1) implant materials, 2) osteoinductive molecules, 3) osteoconductive particles or materials such as bone grafts, and ceramics such as HA, TCP or bioactive glass, etc. Since successful bone repair and regeneration involves various stages where biological and biomechanical factors interact to bring about the ultimate result of bone union, many factors in this complex interplay have to be addressed. Successful bone repair in some pathological conditions or in situations where bone healing may be delayed due to factors such as age, disease or drugs, are more challenging.
• metallic materials afford the highest mechanical properties necessary for use as skeletal prosthetic implants but they are much more rigid than the bone itself with the risk of stress shielding, osteopenia, weakening of the bone and risk of fracture or loosening.
• metals include, titanium and titanium alloy, stainless steel, gold, cobalt-chromium alloys, tungsten, tantalum, as well as similar alloys.
• Titanium is popular in the implant field because of its said superior corrosion resistance, biocompatibility, and physical and mechanical properties compared to other metals.
• recently some particles of titanium have been found in lymph nodes, and thus a search for a better material or radical change in the way that addresses the problem of treatment of bone needs to be developed.
• a significant drawback to titanium implants is the tendency to loosen over time.
• Bone itself is not a static but a dynamic tissue that undergoes turnover and remodeling. Bone is a living tissue whose cells interact with the biomechanical factors to adjust itself into a right remodeling line where either bone formation or bone resorption is the ultimate result in defined area at defined point in time. Even a well-suited implant at the time of surgery (using the principles of carpentry), such an implant can be found to be loosed after some time because of bone resorption. Thus, there is a clear need to address the implant-bone interface in a dynamic scale that involves both the implant and the tissue and timeframe.
• Osteointegration is defined as bone growth directly adjacent to an implant without an intermediate fibrous tissue layer. This type of fixation avoids many complications associated with adhesives and theoretically would result in the strongest possible implant-to-bone bond.
• One common method is to roughen a metal surface creating a micro or macro-porous structure through which bone may attach or grow.
• Implant device designs have been created attempting to produce a textured metal surface that will allow direct bone attachment. US Patents 5,609,635 and 5,658,333 are a couple of examples of these devices.
• HA hydroxyapatite
• beta-TCP beta-tricalcium phosphate
• the HA coatings increase the mean interface strength of titanium implants (see Cook et al., Clin. Ortho. Rel. Res., 232, p. 225, 1988), rapid bone growth and increased osteointegration (see Sakkers et. al., J. Biomed. Mater. Res., 26, p. 265, 1997).
• Optimal HA coating thickness ranges from 50-100 microns (see Thomas, Orthopedics, 17, p. 267-278, 1994).
• Osteoinductive proteins are signaling molecules that stimulate new bone production. These proteins include PDGF, IGF-I, IGF-II, FGF, TGF-beta and associated family members.
• the most effective bone formation-inducing factors are the bone morphogenetic proteins (BMPs).
• the BMPs represent a TGF-beta super-family subset. Over 15 different BMPs have been identified. Most members of this TGF-beta subfamily stimulate the cascade of events that lead to new bone formation (for example U.S. Pat. Nos. 5,652,118; and 5,714,589, reviewed in J. Bone Min. Res., 1993, v8, suppl-2, p. s565-s572). These processes include stimulating mesenchymal cell migration, osteoconductive matrix disposition, osteoprogenitor cell proliferation and differentiation into bone producing cells. Effort, therefore, has focused on BMP proteins because of their central role in bone growth and their known ability to produce bone growth next to implants e.g.titanium (see Cole et. al., Clin.
• a method for the design of a spinal fusion device comprised of wire mesh infused with osteoinductive molecules.
• This device is intended solely for use in spinal fusions and is not designed for use with other prosthetic implants intended for use in other body areas. It is also not designed to be attached to orthopedic implants.
• the goal is for selective beneficial effects on the target, in this case bone cells.
• effective therapies will be those that stimulate osteoblast accumulation, proliferation and differentiation.
• growth regulatory factors in bone including fibroblast growth factor-l (FGF-I), IGF-I and -II, BMPs, TGF ⁇ and PDGF.
• osteoconductive factors are those that create a favorable environment for new bone growth, most commonly by providing a scaffold for bone ingrowth.
• the clearest example of an osteoconductive factor is the extracellular matrix protein, collagen.
• examples of other important osteoconductive materials are also the ceramics such as HA, TCP and bioactive glass.
• Antr-osteolytic bisphosphonates administered orally have the problem of poor GIT absorption and need for higher doses. Gl upset the most common complaint seen with bisphosphonates.
• esophagitis was a potentially serious side effect that occurs in a small percentage of patients.
• 475,000 patients had been treated with alendronate; 1,213 adverse reports had been received and, of these, 199 had adverse effects related to the esophagus.
• the side-effects were rated as serious or severe (de Groen PC, Lubbe DF, Hirsch LJ, et al. Esophagitis associated with the use of alendronate.
• Alendronate is contraindicated in patients with abnormalities of the esophagus that delay esophageal emptying, such as stricture or achalasia (de Groen PC, Lubbe DF, Hirsch LJ, et al. Esophagitis associated with the use of alendronate. N Engl J Med. 1996; 335: 1016-1021).
• These problems thus present a limitation on the use of bisphosphonates according to this mode of therapy and to a certain extent where local problem is addressed, there is a clear need to accomplish the drug delivery locally (to avoid Gl problems).
• US patent 6214049 shows a fibrillar metal wire (e.g. of titanium) attached to a prosthetic device core and which can be coated with biodegradable polymer, which may contain various osteoconductive and osteoinductive factors.
• Osteoclast inhibitors such as bisphosphonate are mentioned as one example.
• DBM demineralized bone matrix
• the DBM composition may also be used as a drug delivery device and it may contain bisphosphonates for this purpose.
• the agent to be delivered is absorbed or otherwise associated with the DBM itself and the role of the polymer is to act as barrier.
• Bone tissue itself is a composite material made up of fibers of collagen running through hydroxyapatite, Ca 5 (P0 4 ) 3 OH. Hydroxyapatite constitutes about 70% of bone tissue. However HA itself is not resorbable and may lead to fibrous tissue formation. ⁇ -TCP & absorbable bioactive glass may be better alternatives.
• matrices have been developed to contain and release bioactive peptides for osteo-induction, bone morphogenetic protein- molecules, as the matrix degrades.
• Organic polymers such as polylactides, polyglycolides, polyanhydrides, and polyorthoesters, which readily hydrolyze in the body into inert monomers, have been used as matrices (see U.S. Pat. Nos. 4,563,489; 5,629,009; and 4,526,909).
• the efficiency of BMP-release from polymer matrices depends on the matrices resorption rate, density, and pore size. Monomer type and their relative ratios in the matrix influence these characteristics.
• Polylactic and polyglycolic acid copolymers, BMP sequestering agents, and osteoinductive factors provide the necessary qualities for a BMP delivery system (see U.S. Pat. No. 5,597,897).
• Alginate, poly(ethylene glycol), polyoxyethylene oxide, carboxyvinyl polymer, and poly (vinyl alcohol) are additional polymer examples that optimize BMP-bone-growth-induction by temporally sequestering the growth factors (see U.S. Pat. No. 5,597,897).
• this approach adds only one factor in bone formation/bone resorption balancing process.
• collagen serves as the natural carrier for BMPs and in a way as an osteoconductive scaffold for bone formation.
• Demineralized bone in which the main components are collagen and BMPs has been used successfully as a bone graft material (see U.S. Pat. No. 5,236,456).
• Proper implant load distribution is yet another characteristic important for correct prosthetic function, such as described for example in U.S. patents Nos.. 5,639,237, and 5,360,446.
• U.S. Pat. No. 5,458,653 describes a prosthetic device coated with a bioabsorbable polymer in specific implant regions to, theoretically, better distribute the load placed upon it.
• Many other endosseous dental implants with shapes attempting to distribute load including helical wires, tripods, screws and hollow baskets have also been used. The clinical success of all these implant types is dependent on placement site, implant fit and the extent of fibrous tissue formation around the implant preventing direct bone contact.
• a method and apparatus for bone tissue management in a mammalian body is presented.
• a primary application of the present invention is to fix fractures and osteotomies, and support a prosthetic multifunctional implant device.
• the implant device comprises a biocompatible bioresorbable polymer as a matrix, a reinforcing biocompatible and bioresorbable structure in close association with said matrix, and at least an anti-osteolytic agent in said matrix.
• the mechanical strength of the implant device can be achieved by the use of self-reinforcement technique or other reinforcing technique.
• the present invention provides a method and a structure for achieving durable bone formation that has a better quality in terms of bone structure, mineral density and function (strength).
• the present invention provides a novel way to augment bone formation for a variety of applications in bone management.
• the implant can comprise: 1) a biocompatible bioresorbable polymer forming a matrix 2) osteoinductive and/or osteroinductive material in said matrix, and 3) an antiosteolytic agent in said matrix.
• one or more molecules that function as nutrients, blood-clotting factors, angiogenic factors, or trace elements, can be included in the matrix.
• the matrix is in close association with a reinforcing structure made of biocompatible bioresorbable polymer, either of the same material or of different material in view of chemical composition.
• the matrix may be the reinforcing structure itself, where the increased strength compared with the raw material is created by means of manufacturing technique, for example orientation and fibrillation of the polymer material so that nearly the whole mass of material has been oriented in desired way (e.g. U.S. Patent No. 4,968,317).
• the term matrix is understood as material capable of incorporating various substances, e.g. active agents such as antiostelytic agents and osteoinductive and/or osteoconductive material, and acting as carrier for them.
• the reinforcing structure and the matrix exist as discrete areas in the implant device, the reinforcing structure possesses greater strength than the matrix, which may be due to different chemical composition, or different physical structure if the chemical composition is the same.
• the reinforcing portion can exist inside the matrix as discrete areas, such as elongate fibers, which may be different in composition or created by self-reinforcing technique form the same material as the matrix. Suitable self-reinforcing techniques creating areas of different physical properties starting from the same raw material within the implant device are good examples of the latter alternative.
• the matrix can further exist as a coating in an implant device where the core is formed of biocompatible bioresorbable polymer material and acts as the reinforcing portion.
• the matrix can also be associated with the implant device as a separate piece, e.g. it may be wrapped around a resorbable implant device as a filament, mesh, sheet, or the like.
• the piece need not necessarily have a reinforcing portion, because the implant device itself imparts strength to the combination, and the separate piece comprises matrix and the antiosteolytic agent.
• the implant may comprise an osteoinductive-protein- sequestering agent comprising monomeric and polymeric units of hyaluronic acid, alginate, ethylene glycol, polyoxyethylene oxide, carboxyvinyl polymer, and vinyl alcohol.
• the agent can be also the polymers collagen or chitosan.
• the polymer may also be composed of a composite of synthetic or naturally occurring polymers comprising collagen and glycosaminoglycan. These materials act as carriers for the osteoinductive proteins and can be in the form of coating on the implant body or filled in pores, openings or channels in the body, which is an advantageous way of incorporating thermally sensitive proteins to the implant device.
• the efficiency of the above-described multifunctional therapy may also be increased and the supplement of the therapy to the area where it is needed to act at, such as around implants sites of metastasis, osteolysis or for fixation of bones can be achieved.
• Fig. 1 shows a first embodiment of the form of the implant device according to the invention
• Fig. 2 shows a second embodiment of the form
• Fig. 3 shows a third embodiment of the form
• Fig. 4 shows one embodiment of the relationship between the matrix and reinforcement
• Fig. 5 shows a second embodiment of the relationship
• Fig. 6 shows a third embodiment of the relationship
• Fig. 7 shows a fourth embodiment
• Fig. 8 shows a fifth embodiment.
• the implant device of the invention has at least the following components:
• Matrix polymer The matrix polymer is biocompatible and bioresorbale and acts as carrier for various agents and materials that contribute to the multifunctionality of the implant.
• Resorbable polymers that can be used are listed e.g. in table 1 of U.S. Patent No. 4,968,317, the disclosure of which is incorporated herein by reference, and those listed in table 1 of European patent 442911 , the disclosure of which is incorporated herein by reference.
• the resorbabe polymers include the following:
• PLA Poly-L-lactide
• PDLA Poly-D-lactide
• PDLLA Poly-DL-lactide
• L-lactide/DL-lactide copolymers L-lactide/D-lactide copolymers Copolymers of PLA 8. Lactide/tetramethylene glvcolide copolymers 9. Lactide/trimethylene carbonate copolymers 10. Lactide/ ⁇ -valerolactone copolymers 11. Lactide/ ⁇ -caprolactone copolymers 12. Polydepsipeptides (glycine-DL-lactide copolymer) 13. PLA/ethylene oxide copolymers
• Matrix polymer is in close association with a reinforcing structure that contributes to the strength of the implant device, which is an important factor in bone fixation and other similar applications.
• a special case is the function of the matrix both as the carrier material and reinforcing structure, due to self-reinforcing technique during the manufacture of the implant device.
• Such techniques are based on mechanical modification of the polymeric raw material, and may include orientation and fibrillation of partly crystalline materials according to above- mentioned U.S. Patent 4,968,317, or mechanical modification of entirely amorphous materials by molecular orientation of the material, according to U.S. Patent 6,503,278, the disclosure of which is incorporated herein by reference.
• the reinforcing structure may be of the same chemical composition as the matrix and be embedded in the same.
• An example of such a composite structure is disclosed e.g. in U.S. Patent No. 4,743,257, the disclosure of which is incorporated herein by reference.
• This structure is also termed "self-reinforced" because of the common origin of both matrix and the reinforcing structure.
• the discrete areas of matrix and reinforcing structure can be 5 composed of chemically different polymers, both being biocompatible and bioresorbable, and the polymer of the reinforcing structure being selected because of its mechanical properties (strength).
• the reinforcing structure can be bioabsorbable0 inorganic materials, for example in the form of fibers of bioabsorbable bioactive glass, as described in U.S. Patent No. 6,406,498, the disclosure of which is incorporated herein by reference.
• the bioactive glass may serve at the same time as osteoconductive material.5
• the reinforcing structure can be the mass of the implant body having a coating which consists of matrix polymer. This matrix polymer acts as carrier for the above-mentioned active agents and materials. It is possible that the body of the implant device is of different0 bioresorbable material and is itself reinforced by some of the above- mentioned techniques.
• the matrix polymer of the coating can be in this case chitosan (a derivative of chitin) for example.
• the matrix polymer acting as carrier can be, alternatively to or additionally to being in the form of coating, filled in pores, channels or openings of the implant5 body.
• the reinforcing structure may be an implant body on which the matrix polymer containing the above-mentioned active agents is fitted as a separate material piece, for example by winding, wrapping etc.0
• the matrix may be in this case a filament, mesh, sheet, or the like, relatively flexible construction.
• the structure of the implant body may be reinforced by any technique discussed above.
• Bisphosphonates are structural analogs of pyrophosphates. They have a pharmacologic activity specific for bone, due to the strong chemical affinity of bisphosphonates for hydroxyapatite, a major inorganic component of bone (see also Watts WB:Bisphosphonates therapy for postmenopausal osteoporosis. South Med J. 1992;85(Suppl):2-31 ).
• Bisphosphonates have the following general formula:
• Substitution of different side chains for hydrogen at locations R ⁇ and R 2 changes the in vitro potency and side effect profile of the compound.
• Short alkyl or halide side chains e.g., etidronate, clodronate characterize first generation bisphosphonates.
• Second generation bisphosphonates include aminobisphosphonates with an amino- terminal group (e.g., alendronate and pamidronate).
• Tiludronate has a cyclic side chain, not an amino terminal group, but is generally classified as a second-generation compound based on its time of development and potency.
• Third generation bisphosphonates have cyclic side chains (e.g., risedronate, ibandronate, zoledronate).
• bisphosphonates include incardronate (cimadronate), olpadronate, piridronate, minodronate, neridronate, EB-1053 and YH529.
• bisphosphonate includes acids, salts, esters, hydrates and other solvates.
• Any bisphosphonate mentioned above can be used in the matrix 5 polymer. It is also possible that two or more different types of bisphosphonates are used in the same implant device.
• the osteoconductive material that is used in the implant device can be any factor known to create a favorable environment for new bone growth, most commonly by providing a scaffold for bone ingrowth.
• the osteoconductive factors that can be used is the extracellular matrix protein, collagen. Examples of other important osteoconductive factors
• HA hydroxyapatite
• TCP beta- tricalcium phosphate
• bone graft autogenic, allogenic or xenogenic bone graft
• the osteoinductive material that is used in the implant device can be any osteoinductive protein that is known to stimulate new bone production. These proteins include PDGF, IGF-I, IGF-II, FGF, TGF- 25 beta and associated family members. The most effective bone formation-inducing factors are the bone morphogenetic proteins (BMPs). Angiogenic factors such as VEGF, PDGF, FGF etc. can also be incorporated to enhance / maintain bone formation process where suitable.
• BMPs bone morphogenetic proteins
• Angiogenic factors such as VEGF, PDGF, FGF etc. can also be incorporated to enhance / maintain bone formation process where suitable.
• Implant device can take any form known in surgery in connection with bone repair and healing (fixation, regeneration/generation, augmentation). It can be in the form of screw, nail, pin, bolt, plate, rod, mesh, scaffold or filament or some combination of the above structures, in general any stiff or tough structure having sufficient strength over the required period of time after being placed in contact with a bone. It can be shapeable to desired form by bending (for example a plate) to fit the site during the operation, or flexible but of sufficient tensile strength, such as a filament. Further, the device can have a closed surface or certain porosity or holes passing through.
• Fig. 1 shows a generally rod-shaped implant device, whose special shapes are screw and nail, which can be used as fixation devices for example.
• Fig. 2 shows a plate-shaped implant device.
• Fig. 3 shows a filament, of which a mesh (here in the form of woven fabric), or a thread or cord (shown in cross-section) can be formed.
• Fig. 4 shows a device where discrete reinforcing elements are embedded in the matrix.
• Fig. 5 shows a device in cross-section where a coating of matrix polymer exists on the implant body.
• Fig. 6 shows the alternative where channels inside an implant body are filled with matrix polymer. The same idea applies to implants where the body comprises pores or openings, which do not necessarily pass through the whole body.
• Fig. 7 shows the alternative where a matrix polymer is between filaments in a bundle (the polymer may also surround the bundle as a coating).
• Fig. 8 shows the alternative where a flexible structure comprising the matrix polymer is wrapped around an
• the antiosteolytic agent can be in the matrix polymer in the coating, in the matrix polymer filling the channels, pores or openings, or in the matrix polymer between or around the filaments.
• the rest of the implant (the body or the filaments) is of another biocompatible bioresorbable material, preferably of another biocompatible bioresorbable polymer, which in turn may or may not contain reinforcing elements or areas, or may or may not be self-reinforced.
• the rest of implant may contain another active agent.
• the anti-osteolytic agent can also be in the rest of the implant, in which case this portion is of biocompatible bioresorbable polymer, which in turn contains reinforcing elements or areas, or is self-reinforced.
• the coating (Fig. 5) or the filling material (Fig. 6 or 7) may contain another active agent.
• the implant device in one embodiment may have a composite of mesh and stem, where the stem can have the anti-osteolytic agent in a matrix.
• a composite is a joint prosthesis, which is disclosed in U.S. Patent No. 6,113,640, where the fixation parts serving to fix the prosthesis to the bone could have the antiosteolytic agent.
• osteoconductive and/or osteoinductive material need not necessarily be in the same matrix as the antiosteolytic agent, but they can be in another matrix phase but in the same implant device.

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